fix(deps): upgrade next-themes to ^0.4.6 for React 19 compatibility (#125)

Upgraded `next-themes` from `^0.3.0` to `^0.4.6` to resolve compatibility issues with React 19.
The previous version (`0.3.0`) does not support React 19, which caused conflicts.

Changes:
- Updated `package.json` dependency: `"next-themes": "^0.4.6"`
- `bun.lockb` updated accordingly.

package.json

@@ -43,7 +43,7 @@
         "jotai-zustand": "^0.6.0",
         "lucide-react": "^0.454.0",
         "luxon": "^3.5.0",
-        "next-themes": "^0.3.0",
+        "next-themes": "^0.4.6",
         "prettier-plugin-tailwindcss": "^0.6.11",
         "react": "^19.0.0",
         "react-dom": "^19.0.0",